1. Field of the Invention
This invention relates generally to a monitor assembly for monitoring the status of a cooling system. More particularly, it relates to an improved monitor assembly and method for monitoring the cooling operation of a cooling system utilized in conjunction with integrated circuit assemblies.
2. State of the Prior Art
The use of cooling systems for removing heat generated by operational systems has long been known. In particular, it has been known to utilized differing types of cooling systems in conjunction with electronic equipment. Through the years, cooling systems have been developed that rely on the flow of air, the flow of other coolant fluids such as water, or the flow of other refrigerants, for transfer and removal of heat energy generated by the system. This use of air flow past electronic circuits provides a relatively simple and straight forward approach to the transfer of heat and the cooling of the electronic circuits in the system. Air flow systems have been known for some time, and it has been recognized that it is desirable to sense the temperature of the air flow stream for attempting to determine that it is at a temperature that will provide adequate cooling. One system of monitoring is to place a thermostat in the stream of air in the vicinity of the air outlet, thereby sensing the temperature of the air after having passed over the electronic components. Mechanical thermostats have a relatively wide-range tolerance, for example in the order of plus or minus three degrees Centigrade. For electronic components that could not tolerate wide temperature ranges of operation, it was necessary to install the components less densely packaged than what otherwise would be allowed for a more precise temperature sensing system. Further, the use of different electronic components within a system often causes a wide range of temperatures within the system due to the differing heat generation characteristics of the various components. As the air flow passed over such differing components, it will be heated accordingly, and the differing air flows are ultimately mixed together at the outlet. Accordingly, when only sensing at the outlet it can be seen that hot spots can occur within the system to the level of causing damage or destructions of electronic components, without necessarily providing a sufficient rise in temperature at the outlet that is capable of being sensed by standard thermostat structures.
As electronic components have been miniaturized, and packaging techniques have led to ever-increasing component densities, the use of air flow for cooling often times does not provide adequate heat transfer. This can be so when the packaging does not permit adequate cooling, even if the air is chilled before entering the system. For example with integrated circuit packages closely packed on printed circuit boards, and the printed circuit boards closely arranged in connector housings, it is often necessary to provide metalic heat exchangers in cooperation with a liquid cooling system. In such systems, it then is important to form a close thermal contact between the components to be cooled and the heat exchanger, thereby permitting the heat to be dissipated into the fluid coolant. Such a cooling system and thermal interface is described in U.S. Pat. No. 4,155,402 to Anthony H. Just, and assigned to the assignee of the present invention. Attempts to monitor the cooling system operation have often involved sensing the fluid temperature at the outlet, or at the manifold, by temperature sensors that sense the fluid temperatures. As previously mentioned, it is recognized that different heat generating components will be often times arranged within the system, and may be tending to cause hot spots. As the coolant fluid passes such hot spots, it will be raised in temperature, but when that coolant fluid is mixed with coolant fluid passing other components, may result in a coolant fluid temperature that does not indicate any overheating. Further, should the coolant fluid passage in any part of the system become blocked, the coolant fluid would not raise in temperature at all while the uncooled components are being totally destroyed for lack of proper cooling.
When monitoring the coolant, whether it be air, water, or some other coolant medium, a detected temperature fault or danger condition normally does not isolate the hot spot, and does not particularly aid in maintenance or evaluation of the problem for correction purposes. As integrated circuits are packed in ever-tighter densities, each replaceable assembly is relatively more complex and expensive for fabrication. Accordingly, it is desirable that each assembly be monitored with regard to temperature fault conditions that could lead to damage or destruction of the assembly. Further, it is desirable to provide a monitoring system that identifies the location of the sensed temperature fault condition as an aid for maintenance and repair, and to minimize down time of the system.
The prior art systems for monitoring operation of cooling systems uniformly have the defficiency of attempting to monitor the temperature of the coolant medium. In electronic equipment that has relatively wide ranges of heat dissipation in different parts of a system, all of which are cooled by a common cooling system, this renders it difficult to derive a monitoring system that will monitor proper operation and cooling at different locations in the systems.